But, over weeks or months or even years, the Ca(OH)2 + CO2 from the atmosphere, turns into CaCO3. i.e. given enough time the lime in your mortar turns to limestone again.

- the things you learn on this forum
And I thought all that huffing and puffing had no effect on the mortar - so the bigger the number at your pizza party the tougher your oven becomes - just get them all to breathe out towards the dome

Quote:

By the way, I'm an assayer. Sort of a practical and applied chemistry sorta guy, we don't like to call ourselves chemists.

Has anyone else tried the "calcium aluminoslicate" home brew ? I use it everyday in my countertops as a additive so have access to it so cost is negligible .. Does it make a better refractory mortar then the portland brew?

I guess that's a typo and you mean CaO2 - since although you will expend a lot of CO2 in the oven, breathing alone won't be enough
Mistakes in chemical formulas can lead to unexpected results.
Good luck with your oven
Aidan

No,

that formula is correct, besides, air does contain some CO2, but no CaO2.
I understand the chemical reactions quite well, my problem is my lack of practical experience in building ovens.

Chaps one note of caution about relying on the Hydrated lime to combine with the CO2 in the air to make CaCO3. I reckon its going to take a very long time, especially if its dry. Lets face it, an open bag of lime doesn't "go off" in your garage. I can't really explain it in any sort of logical terms, but I reckon it'd need to be damp to help the reaction along.

In fact, it is known, that even walls built of lime cement in the middle ages are not already completely turned into CaCO3, because of the thickness of those walls.

The reaction is of course controlled by diffusion, which can take a very long time, but in fact, the reaction doesn´t stop as long as there is any Ca(OH)2 left.

Gudday all
One thing about hombrew that strikes me is its "workability"....the stuffs really great to lay bricks with ....not at all like normal mortar. Recon its the reason so many of these fantastic oven builds are turned out by basically mug first timers

I spent a lot of time tracking down materials. I don't know how to translate fireclay (google says Schamotte)

Google is right, but the problem is, that until now I could find Schamotte only as bricks or as refractory mortar, but I think that "fire clay" is not just a high heat mortar, but some kind of clay powder (the same analysis as the bricks, that´s why you could use the dust from your tile saw? But isn´t the analysis of fire bricks just the same as ordinary pottery clay?) without the additives that are in a high heat mortar?

Of course I can find refractory mortar, but I don´t think, this is meant to mix with sand, portland cement or lime?

Here, you can buy fire clay in bags just like mortar. As per the instructions I used it and sand to stick the floor bricks so they can be removed.

Refractory mortar is a mortar mix. It is just like regular mortar for setting bricks or stones except it can take very high heat. It is also stickier (more like 'thinset mortar for setting tiles) and sets up much faster than regular mortar. It is also very expensive, so I made small batches of about 4 litres because I found I could more or less use that amount to set bricks before it started to harden.

I've said it before, and I'll say it again: because of the huge amount of hard work involved in making a pizza over, I would strongly recommend people use the best materials they can get their hands on. It would be a pity to do so much work and end up with a problem because of substandard materials.

So, if I were you and I could get refractory mortar, thats what I would use.

I'm not looking for a debate, but homebrew has a long history of outperforming refractory mortars for our based on the users of this site. I personally demolished my first oven made with home brew to build a larger oven and has to cut the mortar off, it was so strong and hard the bricks broke before it did trying to chip it off. Many users have switched from one to the other at some point in the build, and all prefer the home brew. Refractory mortar is not ideal for pizza ovens for a few reasons. They are made for tiny mortar gaps on square bricks. That is not our situation. Some also require long curing processes at extreme temperatures to be installed to manufacturers specs, this is not possible in our ovens.

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